330 Herschel Poster Session
330.01
Transient Correction for PACS/Herschel Unchopped Spectroscopy
Dario Fadda1, J. D. Jacobson1
1Caltech.
8:00 AM - 7:00 PM
America Ballroom Foyer
We present a technique to correct the long term transients in the signal from unchopped spectroscopy with the PACS instrument onboard the Herschel Space Telescope. This kind of transient occurs every time there is a big jump in flux on the detector and affects the signal approximately for the first 6 minutes. The effect is particularly pronounced in the case of the red array where it can amount up to
20% variation in the response of the array, but it also visible in the case of the blue array. Correcting these transients is critical especially in the case of short observations since this time corresponds to the minimum amount of time allowed in unchopped mode.
330.02
HIGGS: The Herschel Inner Galaxy Gas Survey
Volker Tolls1, C. L. Martin2, HIGGS Team
1Harvard-Smithsonian, CfA, 2Oberlin College.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Herschel Inner Galaxy Gas Survey (HIGGS) is a Herschel Key Project to use the HIFI and PACS instruments to observe [CII], [NII], [OI], [OIII], and high-J CO emission lines in focused regions near the Galactic Center. By separating and evaluating the distinctly different roles of the central nuclear engine, the Galactic Bar, and dynamical stellar and interstellar feedback mechanisms, HIGGS will provide a high-resolution template for the physical processes in galactic nuclei throughout the local universe, in particular those engaged in starburst activity. We will present the current status of our data reduction and analysis of the data taken in September 2010.
Funding for HIGGS has been provided by NASA and time on Herschel by ESA.
330.03
Recent Results from the Herschel Orion Protostar Survey
William J. Fischer1, T. Megeath1, B. Ali2, D. Watson3, M. Puravankara3, R. Vavrek4, C. Poteet1, J. Tobin5, T. Stanke6, A. Stutz7, HOPS team
1University of Toledo, 2NHSC/IPAC/Caltech, 3University of Rochester, 4HSC/ESAC, Spain, 5University of Michigan, 6ESO, Germany, 7MPIA, Germany.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Herschel Orion Protostar Survey (HOPS) is an ongoing 200-hour open-time key project with the Herschel Space Observatory to study protostars in the Orion molecular cloud complex. HOPS is obtaining PACS 70 and 160 micron imaging of 286 Orion protostars and PACS spectroscopy of a subset of 36, sampling the expected peaks of their spectral energy distributions (SEDs). The Herschel data are complemented by Spitzer 3-24 micron photometry and 5-40 micron spectroscopy, high angular resolution near-IR imaging with Hubble and ground-based telescopes, and millimeter observations of the surrounding gas. With these combined data we can determine the fundamental properties (multiplicity, gas infall rate, bolometric luminosity, outflow cavity geometry) of a large sample of protostars in a single cloud complex. With far-IR imaging and 1.6-160 micron SEDs for 171 protostars and 55-200 micron spectroscopy for 10 protostars expected to be in hand by mid-March 2011, we will present a selection of recent results.
330.04
A Herschel SPIRE Study of M81: Separating Cold and Warm PAH Emissions
Nanyao Y. Lu1, G. Bendo2, VNGS Team
1Caltech, 2Imperial College, United Kingdom.
8:00 AM - 7:00 PM
America Ballroom Foyer
We study correlations among three distinct dust emission components in the interstellar medium of the galaxy M81 at a sub-kpc resolution: (a) I_8, the surface brightness of non-stellar emission in Spitzer IRAC 8 um band, dominated by the so-called PAH emission features, (b) I_24, that of hot continuum emission in Spitzer MIPS 24 um band, arising from small dust grains powered mainly by young stars, and (c) I_500, that of cold dust continuum emission in Herschel SPIRE 500 um band, from large dust grains heated by evolved stars. Both I_8/I_500 and I_24/I_500 ratios increase towards active star-forming regions, consistent with the view that both (a) and (b) are correlated with current star formation. But as I_24/I_500 decreases to zero, I_8/I_500 approaches to a finite, positive value of 0.05 or greater. This implies that 57% of the 8 um non-stellar emission is "cold," arising from regions, where the 24 um emission is relatively insignificant. Since it is likely that the fraction of this cold component in the PAH emission varies from galaxy to galaxy, making the PAH luminosity a rather poor star formation tracer in general.
330.05
Active Galactic Nuclei, Host Star Formation, and the Far Infrared
Aden R. Draper1, D. R. Ballantyne1
1Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology.
8:00 AM - 7:00 PM
America Ballroom Foyer
Telescopes like Herschel and the Atacama Large Millimeter/submillimeter Array (ALMA) are creating new opportunities to study sources in the far infrared (FIR), a wavelength region dominated by cold dust emission. Probing cold dust in active galaxies allows for study of the star formation history of active galactic nuclei (AGN) hosts. The FIR is also an important spectral region for observing AGN which are heavily enshrouded by dust, such as Compton thick (CT) AGN. By using information from deep X-ray surveys and cosmic X-ray background synthesis models, we compute Cloudy photoionization simulations which are used to predict the spectral energy distribution (SED) of AGN in the FIR. Expected differential number counts of AGN and their host galaxies are calculated in the Herschel bands. The expected contribution of AGN and their hosts to the cosmic infrared background (CIRB) is also computed. Multiple star formation scenarios are investigated using a modified blackbody star formation SED. It is found that FIR observations at 350 and 500 um are an excellent tool in determining the star formation history of AGN hosts. Additionally, the AGN contribution to the CIRB can be used to determine whether star formation in AGN hosts evolves differently than in normal galaxies. AGN and host differential number counts are dominated by CT AGN in the Herschel-SPIRE bands. Therefore, X-ray stacking of bright SPIRE sources is likely to disclose a large fraction of the CT AGN population.
330.06
Molecular Collisional Excitation Computations for Modeling of FIR/Submm Observations
Jeff Nolte1, B. H. Yang2, W. el-Qadi1, S. Fonseca dos Santos3, T. G. Lee4, N. Balakrishnan3, R. C. Forrey5, P. C. Stancil1, G. Shaw6, N. P. Abel7, R. L. Porter1, D. Quan8, G. J. Ferland8, D. R. Schultz9, P. A. M. van Hoof10
1University of Georgia, 2Texas Tech University, 3University of Nevada, 4Auburn University, 5Penn State University, 6Centre for Excellence in Basic Science, India, 7University of Cincinnati, 8University of Kentucky, 9Oak Ridge National Laboratory, 10Royal Observatory of Belgium, Belgium.
8:00 AM - 7:00 PM
America Ballroom Foyer
As most of the gas in the Universe is not in thermal equilibrium, accurate modeling and interpretation of observations requires understanding of a variety of collisional processes. Rate coefficients describing such processes can usually be measured and/or calculated, but the enormous enhancements in the spectral line resolution and sensitivity expected from ALMA, SOFIA, Herschel, and other FIR/submm telescopes place unquenchable demands on the collisional data. As a consequence, the construction of reliable collisional data sets for astrophysical/astrochemical modeling faces a number of challenges: i) Due to the voluminous quantity of required data, theory must provide the bulk of the results with experiment serving as benchmarks. ii) The accuracy of the scattering calculations are directly dependent on the reliability and availability of the quantum chemical data. iii) Database construction requires consistent and appropriate funding which is typically lacking. We review these issues in the context of our ongoing collaborative work on computations of rovibrational excitation of H_2, HD, CO, H_2O, CO_2, NH_3, and CH_4 due to H, He, and H_2 collisions and their role in the modeling of various astrophysical environments.
This work was partially supported by NASA grants NNG05GD81G, NNG06GC94G, NNX07AP12G, and NNX10AD56G, and NSF grants PHY-0554794, PHY-0855470, PHY-0854838, and AST-0607733.
331 Instrumentation: Space Missions & Related Topics Poster Session America Ballroom Foyer
331.01
Updated Status and Performance for the Cosmic Origins Spectrograph
Justin Ely1, D. Massa1, M. Wolfe1, C. Proffitt2, C. Oliveira1, A. Aloisi1, B. York1, R. Osten1, D. Sahnow3, V. Dixon3, T. Ake2, W. Zheng3, K. Azalee Bostoem1, S. Niemi1, K. Hart4
1STScI, 2STScI/CSC, 3JHU, 4UMD.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Cosmic Origins Spectrograph (COS) was installed on the Hubble Space Telescope (HST) in May 2009. COS is designed to perform high-sensitivity, medium- and low-resolution spectroscopy of astronomical objects in the 1150-3200 Å wavelength range. COS significantly enhances the spectroscopic capabilities of HST at ultraviolet wavelengths, providing observers with unparalleled opportunities for observing faint sources of ultraviolet light. Provided here is an update on some aspects of detector performance and current calibration projects from the second half of Cycle 17 and through the first half of Cycle 18. Included are discussions on the analysis of gain sag and its effects, changes in the dark current and the time dependent sensitivity, and updates to the NUV and FUV flatfields.
331.02
Updated Status and Performance of the Space Telescope Imaging Spectrograph
Michael A. Wolfe1, W. V. Dixon2, E. Mason3, C. Proffitt4, A. Aloisi1, C. Oliveira1, R. C. Bohlin1, R. Osten1, K. A. Bostroem1, W. Zheng2, I. Pascucci3, S. Niemi1, B. York1, P. Sonnentracker3, R. Diaz1, J. C. Ely1
1STScI, 2JHU, 3STScI/ESA, 4STScI/CSC.
8:00 AM - 7:00 PM
America Ballroom Foyer
A description is provided of the overall performance of the Space Telescope Imaging Spectrograph after Cycle 17 and through the first half of Cycle 18. Most aspects of performance are still found to be consistent with extrapolations of the trends seen during Cycle 17 calibrations. Many of the characteristics of the instrument have changed over time, and we present here an update on its current performance based on the latest Cycle 18 calibration observations. We discuss changes in the CCD and MAMA dark currents, provide updates on the sensitivity of STIS modes, echelle blaze function, discuss changes, if any, in number of hot pixels, flat fields, charge transfer inefficiency, read noise, and spurious charge.
331.03
An All Reflective Ultraviolet Integral Field Spectrometer
Timothy Cook1, S. Chakrabarti1
1Boston Univ..
8:00 AM - 7:00 PM
America Ballroom Foyer
We present the design of a new wide field integral field spectrometer. The system uses an astigmatic all reflective image slicer which is suitable for use in the far ultraviolet and is compact enough for sounding rocket or small satellite applications. We detail the design and simulated results for a number of observing programs.
331.04
Laser Stabilization and Material Studies for the Laser Interferometer Space Antenna (LISA)
Amanda Cordes1, G. Mueller1, D. B. Tanner1, P. Arsenovic2, J. Livas2, A. Preston2, J. Sanjuan1, S. A. Reza1, S. Mitryk1, J. Eichholz1, A. Spector1, D. Donelan1, R. Spannagel3, D. Korytov1
1University of Florida - Physics Department, 2Goddard Space Flight Center, 3University of Applied Sciences Konstanz, Germany.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Laser Interferometer Space Antenna (LISA) is a joint NASA/ESA project designed to detect gravitational waves. The University of Florida (UF) LISA laboratory is currently implementing and testing much of the instrumentation of the LISA interferometer measurement system to ensure the success of the upcoming LISA mission. LISA will consist of three spacecraft (SC) orbiting the sun in an equilateral triangular formation with an arm length of 5 Gm. Each SC will house two free floating proof-masses, two laser interferometer benches and two telescopes to transmit the laser light between SC. The constellation will trail the earth by 20° and be tilted by 60° with respect to the ecliptic. LISA is designed to detect low frequency gravitational waves (GWs) in the frequency band of .1mHz to 1 Hz with optimal strain sensitivity of 10^-21/sqrt(Hz) at 3 mHz corresponding to sources such as galactic binaries and black hole mergers. The dimensional stability of all optical paths within each interferometer arm is imperative for the success of LISA. Changes larger than a pm/sqrt(Hz) in the distance between optical components in the interferometer would limit the sensitivity of LISA. The UF LISA lab is testing materials with low thermal expansion coefficients which could be used as spacer materials for the telescopes or as the base material for the optical benches. Together with the LISA group at Goddard Space Flight Center we currently also test the dimensional stability of a silicon carbide telescope structure for LISA. The most demanding requirement on material stability is the requirement for the optical reference cavity which is used as the frequency reference for the lasers. We currently test different sensing schemes for the laser frequency stabilization system of LISA and will also report about these experiments. This work is supported by NASA Contract #00078244 and NASA Grant NNX08AG75G.
331.05
What Is New For WFC3 Astrometric Calibration?
Vera Kozhurina-Platais1, L. Petro1, C. Cox1, M. Dulude1
1STScI.
8:00 AM - 7:00 PM
America Ballroom Foyer
Already two years on orbit, the status of geometric distortion for the HST WFC3 camera is continuously updated along the following lines: 1)extending of astrometric calibration to additional UVIS and IR filters; 2) improving of accuracy for absolute astrometry; 3) implementing of filter-dependency in geometric distortion for
additional reference files (DGEO) to be used in the STScI Multidrizzle
software; 4) monitoring the variations of skew parameter such as non-perpendicularity of the coordinate axes. Our goal is to establish
a single WFC3 geometric distortion parameter, which can reliably
characterize the stability of WFC3 over time, HST roll-angle, and
scale changes from filter to filter.
331.06
The Bragg Reflection Polarimeter On the Gravity and Extreme Magnetism Small Explorer Mission
Ryan Allured1, P. Kaaret1, GEMS Team
1University of Iowa.
8:00 AM - 7:00 PM
America Ballroom Foyer
The strong gravity associated with black holes warps the spacetime outside of the event horizon, and it is predicted that this will leave characteristic signatures on the polarization of X-ray emission originating in the accretion disk. The Gravity and Extreme Magnetism Small Explorer (GEMS) mission will be the first observatory with the capability to make polarization measurements with enough sensitivity to quantitatively test this prediction. Students at the University of Iowa are currently working on the development of the Bragg Reflection Polarimeter (BRP), a soft X-ray polarimeter, sensitive at 500 eV, that is the student experiment on GEMS. The BRP will complement the main experiment by making a polarization measurement from accreting black holes below the main energy band (2-10 keV). This measurement will constrain the inclination of the accretion disk and tighten measurements of black hole spin.
331.07
Integration and Testing of the Micro-X Rocket Payload
Enectali Figueroa-Feliciano1, Micro-X Collaboration
1Massachusetts Institute of Technology.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Micro-X instrument is a rocket borne, X-ray imaging spectrometer planned for launch in October 2011. An array of 128 Transition Edge Sensors (TESs) on a 600 micron pitch will observe incoming photons in the 0.2-3 keV energy band with an energy resolution of 2-4 eV at 1 keV. X-rays will be focused onto the TES array by a conically approximated Wolter optic with an effective area of 300 cm^2 giving the instrument a field of view of 11.8 arcmin. This performance will constitute a substantial improvement over current non-dispersive detectors for X-ray spectroscopy of extended sources and will be the first demonstration of a TES-based microcalorimeter in space. The TESs will utilize the 50 mK stage of an Adiabatic Demagnetization Refrigerator (ADR) as a heat bath, and will be read out by a SQUID time division multiplexer. The first flight of the Micro-X instrument will observe the Puppis A supernova remnant. Future targets include the core of the Virgo cluster and the Cas A supernova remnant. We describe the design, development progress and performance testing of the instrument.
331.08
Status and Calibration of the HST Wide Field Camera 3
John W. MacKenty1, WFC3 Team
1STScI.
8:00 AM - 7:00 PM
America Ballroom Foyer
Wide Field Camera 3 is the most used science instrument on HST since its installation in May 2009 during Servicing Mission 4. This presentation reviews its in-flight performance and calibration with particular attention to topics relevant to Cycle 19 Phase 2 proposers. The new capability for Charge Injection in the UVIS channel to mitigate radiation damaged induced charge transfer inefficiency will be discussed. Results from recent tests to commission a capability to perform spatial scans to enable higher S/N spectroscopy of bright target will presented. Ongoing improvements to the photometric, flat field, and spectroscopy calibrations will be summarized.
331.09
Get Better Resolution by Throwing Away Light: Non-Redundant Masking in Optical Systems
Alexandra Greenbaum1, A. Sivaramakrishnan2
1Rensselaer Polytechnic Institute, 2Space Telescope Science Institute.
8:00 AM - 7:00 PM
America Ballroom Foyer
Astronomers strive for clearer images with finer detail, better resolution. Particularly with the last decade’s increasing interest in exoplanets, the burden lies on the instruments to provide the eye into the backyard of other planetary systems. Non-redundant Masking provides over two-fold better resolution than traditional imaging, acting as a multi-baseline intereferometer instead of a circular aperture. Analyzing intereferometric data is achieved through the science of Fraunhoffer diffraction (optics) and Fourier transforms. Preliminary analysis of near-IR data from the Project 1640 Integral Field Spectrograph (Hinkley et al. 2009) on the Palomar Hale yields a directly detected companion in a known spectroscopic binary. Additionally, laboratory optics of faint companions to be imaged on AMNH’s NRM testbed with a mask designed for the JWST FGS Tunable Filter Imager were developed. A promising two-pinhole method of light attenuation, where no additional polarization or scattering is introduced, was modeled theoretically and implemented in hardware.
This research was funded by the NSF REU program at the American Museum of Natural History summer 2010.
331.10
Laser Noise Stabilization, Processing, And Extraction Simulations For The Lisa Mission At The University Of Florida.
Yinan Yu1, S. Mitryk1, D. Sweeney1, A. Spector1, J. Eichholz1, D. Donelan1, A. Preston2, J. S. Munoz1, S. Azer1, D. Tanner1, G. Mueller1
1University of Florida, 2Goddard Space Flight Center.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Laser Interferometer Space Antenna (LISA) Mission will strive to measure gravitational radiation in the frequency range from 1 Hz to 0.1 mHz from black hole mergers and other compact objects. Three spacecraft (SC) in a nearly equilateral triangular formation with an arm-length of 5.0 ± 0.025 Gm form the space-based interferometer. Differential length changes between free-floating proof-masses will be measured to an accuracy of 40 pm/√Hz using one-way laser phase measurements between lasers on adjacent SC. Accurately reconstructing the differential arm-length and extracting the gravitational wave signals from the photo-detector beatnotes depends on the performance of the laser pre-stabilization system, the ability of time-delay interferometry (TDI) to cancel the additional laser phase noise, the accuracy of the distance-ranging measurement between the SC, the sensitivity of the laser beatnote phase measurement, and the quality of the inter-SC clock transfers. The University of Florida Laser Interferometry Simulator (UFLIS) emulates the LISA interferometry using LISA-like laser noise sources, electronic replications of inter-SC laser phase delays, and µcycle/√Hz phase measurements of MHz-frequency laser beat-notes to test LISA interferometry. This work is supported by NASA Grant #NNX08AG75G.
331.11
Improvements to Warm IRAC/Spitzer Space Telescope Operations
Sean J. Carey1, J. Ingalls1, W. Glaccum1, J. Krick1, J. Stauffer1, S. Willner2, J. Hora2, L. Storrie-Lombardi1
1Spitzer Science Center / Caltech, 2Harvard-Smithsonian Center for Astrophysics.
8:00 AM - 7:00 PM
America Ballroom Foyer
We present current and future planned modifications to the operations of the Spitzer Space Telescope to facilitate science during the ongoing warm Spitzer mission. The 3.6 and 4.5 micron cameras of the IRAC instrument have been operating flawlessly and almost identically as they did in the cryogenic mission since the start of warm science operations in August 2009. The operations of the instrument and spacecraft continue to evolve as attempts are made to optimize observations for the expanding field of exoplanet transit studies. A significant improvement in the pointing stability was made in September 2010 by modifying the cycling temperatures of a spacecraft battery heater. Experiments aimed at improving the pointing drift and improving initial pointing accuracy are currently being planned or executed. To permit useful operations beyond 2013, methods of improving onboard data compression are being explored to mitigate the decreased bandwidth of data downlinks with Spitzer's increasing distance from Earth. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.
331.12
Two-Dimensional Spectroscopy with the Cosmic Origins Spectrograph
Steven V. Penton1, D. Sahnow2, K. France1
1Univ. of Colorado, 2Johns Hopkins University.
8:00 AM - 7:00 PM
America Ballroom Foyer
The circular aperture of HSTs' Cosmic Origins Spectrograph (COS) is 2.5" in diameter, but transmission extends out to a 4" diameter. The NUV MAMA and the FUV microchannel plates image the sky over the full extent of the transmission. The cross-dispersion plate scale of the NUV channel is 0.02" and is 0.1" for the FUV channel. In this presentation we will discuss the capabilities and limitations of performing two-dimensional spectroscopy, in the cross-dispersion direction, with COS. In particular, we will discuss FUV detector effects, such as fixed pattern noise, gain sag, and Y walk, and the latest techniques for their correction.
331.13
Scheduling Predictability and Scientific Productivity of Current HST Pure Parallel Observations
Galina Soutchkova1, A. Patterson2, W. Workman2
1STScI, 2CSC/STScI.
8:00 AM - 7:00 PM
America Ballroom Foyer
The new system of scheduling of HST parallel observations is proving to be quite efficient in accomplishing scientific objectives of parallel programs and has been already appreciated by the observers.
In this report we describe the components of the process that ensures scheduling predictability of parallel observations and its importance for the observer's effort to maximize the scientific return of the programs. We show the possibilities for the observer to modify the original program throughout the entire HST observing Cycle, which would allow him/her to achieve the program's objectives despite unavoidable cases of failure or changes of the associated prime programs.
331.14
Space Qualified Building Blocks For NASA Explorer-class Optical Telescopes And Instruments: Heritage Technology Used In WISE, JWST Kepler, Spitzer And Other Contemporary Spaceborne Missions
Anthony B. Hull1, M. Schwalm2, A. Clarkson3, J. Barentine1
1L-3 Integrated Optical Systems: Tinsley, 2L-3 Integrated Optical Systems: SSG, 3L-3 Integrated Optical Systems: Brashear.
8:00 AM - 7:00 PM
America Ballroom Foyer
Spaceborne missions require that all flight components be rated at a high Technology Readiness Level (TRL) to control risk, schedule and cost. Highest TRL ratings are given to hardware that has been flown successfully. L-3 Integrated Optical Systems (IOS, comprised of the former Tinsley, SSG and Brashear) has participated development of a significant number of successful optical telescope assemblies and optical instruments for exacting spaceborne requirements and environments. From these come established methods and hardware elements that references this IOS flight experience with associated high TRL, and which may be partially or wholly used for future missions.
331.15
Three Dimensional Orbit By Implementation Of Spacecraft Stability Analysis Making A Halo Orbit About CN Lines
Cyrus Nejat1
1University of Southern California.
8:00 AM - 7:00 PM
America Ballroom Foyer
In this study, the main discussion emphasizes on three dimensional orbit and the spacecraft stability analysis based on linearizing of equations of motion. The main points are to monitor the entire solar
system and to determine the stability of the spacecraft on a halo orbit around CN lines (Cyrus Nejat lines). After the determination of instability of the system, the gain matrix is used to stabilized the system based on zeroth order optimization techniques. Root Locus, and Nyquist theorems are used to demonstrate the system is stable based on the procedure that it had been used. The controllability and observability of the system have been evaluated in order to determine the possibility of having stabilized system by using PD method. The results show stability condition after using gain matrix and illustrate promising features for the initial values that have been used to stabilize the system.
332 Intergalactic Medium & QSO Absorption Line Systems Poster Session America Ballroom Foyer
332.01
HST/COS Probes the Starburst Wind of NGC 2611
Brian A. Keeney1, J. T. Stocke1
1Univ. of Colorado.
8:00 AM - 7:00 PM
America Ballroom Foyer
We present moderate-resolution Cosmic Origins Spectrograph (COS) far-UV spectra of the QSO PG 0832+251, which probes the starburst galaxy NGC 2611 (z = 0.0175) along its minor axis at a distance of 2.5 arcmin (54 kpc in projection). An 11-ksec FUSE spectrum of PG 0832+251 revealed Lyβ and O VI absorption associated with NGC 2611; our COS G130M and G160M spectra span the wavelength range 1136-1797 Ǻ with a spectral resolution of ~18,000 and cover low- (H I, O I, N I, C II, Si II, Fe II, S II, Al II) and intermediate-ions (Si III/IV, C IV, N V) associated with NGC 2611. Probing starburst winds at appreciable distances along the galaxy's minor axis is the most straightforward way of determining whether gas entrained in the wind will escape the galaxy's gravitational potential to enrich the intergalactic medium, since absorption-line studies which use the starburst continuum itself as a background source suffer from large ambiguities in the location of the absorbing gas. However, the interpretation of the absorption lines in the PG 0832+251 spectrum are complicated by the presence of a small galaxy group, of which NGC 2611 is the largest member.
332.02
Mid-Infrared Observations of Possible Intergalactic Star Forming Regions in the Leo Ring
Mark Giroux1, B. Smith1, C. Struck2
1East Tennessee State Univ., 2Iowa State University.
8:00 AM - 7:00 PM
America Ballroom Foyer
Within the Leo group of galaxies lies a gigantic loop of intergalactic gas known as the Leo Ring. Not clearly associated with any particular galaxy, its origin remains uncertain. It may be a primordial intergalactic cloud; alternatively, it may be a collision ring, or have a tidal origin. Combining archival Spitzer images of this structure with published UV and optical data, we investigate the mid-infrared properties of possible knots of star formation in the ring. These sources are very faint in the mid-infrared compared to star forming regions in the tidal features of interacting galaxies. This suggests they are
either deficient in dust, or they may not be associated with the ring.
332.03
New Constraints On Gas Properties From The Fuv: Oiv + Ovi Absorbers
Joe Meiring1, T. Tripp1, J. Tumlinson2, C. Thom2, J. Prochaska3, J. Werk3, C. Howk4, N. Lehner4
1U Mass, 2STSCI, 3UCSC, 4Notre Dame.
8:00 AM - 7:00 PM
America Ballroom Foyer
Despite the increasing numbers of O VI absorbers observed, the ionization mechanisms of these systems is still not well understood. Both photo and collisional ionization seem to play roles in the ionization of the gas in these systems. In order to place constraints on the baryon fractions as traced by O VI absorbers, the ionization mechanisms must be well understood. Part of the confusion is due to the lack of adjacent ionization states of ions in existing spectra. We present new observations with the COS spectrograph of several absorbers at z>0.4 that have O II, OIII, OIV, and OVI absorption lines. With these adjacent ionization stages we can much more tightly constrain the physical conditions in the gas. Here, we present voigt profile fits to these lines, as well as the results of photo and collisional ionization modeling.
332.04
High Redshift Science With The FIRE IR Spectrograph At Magellan
Robert A. Simcoe1, M. Matejek1, K. Cooksey1, A. Burgasser2, J. Bochanski3, R. Bernstein4
1MIT, 2UCSD, 3Penn State, 4UCO/Lick Observatories.
8:00 AM - 7:00 PM
America Ballroom Foyer
FIRE (the Folded-port Infrared Echellette) is a new near-infrared spectrometer for the 6.5 meter Magellan Baade telescope; it operates at R=6000 and covers the 0.82-2.5 micron band. One of FIRE's primary science drivers is to perform detailed observations of chemical abundances in the IGM at z > 5 as a proxy for early star formation, feedback and enrichment. This contribution describes results from the first year of FIRE's operation, including measurements of the C IV abundance at z > 5.5 and the Mg II abundance at 2.5 < z < 6. FIRE's construction and early science observations are supported by the National Science Foundation, and the Curtis Marble Fund at MIT.
333 Astronomy Education & Public Outreach Poster Session America Ballroom Foyer
333.01
Dark Energy is “Dying” and Other Student Ideas About Cosmology
Janelle M. Bailey1, K. Coble2, G. L. Cochran3, R. Sanchez1, D. Larrieu2, V. L. Hayes2, M. Nickerson2, L. R. Cominsky4, K. M. McLin4
1Univ. Nevada, Las Vegas, 2Chicago State Univ, 3Florida International Univ, 4Sonoma State Univ.
8:00 AM - 7:00 PM
America Ballroom Foyer
Determining the range and frequency of “alternative conceptions” is an important first step to improving instructional effectiveness. Modern topics in astronomy, such as cosmology, are of primary interest to many educators and students, but we are only beginning to understand students’ alternative conceptions in this area. Through analysis of pre-instructional open-ended surveys (N > 500), our research group is attempting to classify students’ ideas about concepts important to modern cosmology, including the structure, age, and evolution of the universe; dark matter and dark energy; and the Big Bang. Survey responses, analyzed through an iterative process of thematic coding, reveal a number of alternative conceptions. For example, students frequently conflate structure terms such as solar system, galaxy, and universe or do not understand the relationship between the terms; believe the universe to be infinitely old; and may not be aware of dark matter or dark energy. This work was supported by NASA ROSES E/PO Grant #NNXlOAC89G, as well as by the Illinois Space Grant Consortium and National Science Foundation CCLI Grant #0632563 at Chicago State University and the Fermi E/PO program at Sonoma State University.
333.02
Investigating Student Understanding of the Universe: Dark Matter
Melissa Nickerson1, K. Coble1, G. L. Cochran2, V. L. Hayes1, C. T. Camarillo1, J. M. Bailey3, K. M. McLin4, L. R. Cominsky4
1Chicago State University, 2Florida International University, 3University of Nevada, 4Sonoma State University.
8:00 AM - 7:00 PM
America Ballroom Foyer
Student pre-course surveys reveal that students who enter the classroom have little knowledge or understanding of the concept of dark matter (DM). At Chicago State University, we enthusiastically introduce this concept to students through interactive tutorials and hands-on inquiry-based laboratory activities. We have analyzed pre and post laboratory assessments and student interviews to determine the extent to which these tutorials have helped our students to gain a more robust understanding of the topic. The results of this work will be presented. This project is a part of our efforts at CSU to reform our introductory astronomy course. This project is part of a larger study; also see our posters on student ideas about the age and expansion of the universe, the structure of the universe, and perceptions of astronomical sizes and distances. This work was supported by NASA ROSES E/PO Grant #NNXlOAC89G, as well as by the Illinois Space Grant Consortium and National Science Foundation CCLI Grant #0632563 at Chicago State University and the Fermi E/PO program at Sonoma State University.
333.03
Investigating Student Understanding of the Universe: Age and Expansion
Kimberly A. Coble1, G. L. Cochran2, V. Hayes1, M. Nickerson1, C. T. Camarillo1, J. M. Bailey3, K. M. McLin4, L. R. Cominsky4
1Chicago State Univ., 2Florida International University, 3University of Nevada, 4Sonoma State Univ..
8:00 AM - 7:00 PM
America Ballroom Foyer
At Chicago State University we are reforming our introductory astronomy course. As a part of this effort, we seek to bring the tools and advances of recent cosmological research to the classroom by developing curricular materials that support students in learning cosmological topics using real data and cosmological research methods. Analysis of pre-course surveys, pre-course essays, and pre-instructional interviews indicate that students bring to the classroom an array of incorrect ideas regarding the age of the universe. Analysis of assessments, post-instructional interviews, and student comments on laboratory activities indicate that their ideas on this topic have changed to be more in line with scientific evidence. Yet, students still struggle perform the measurements and calculations necessary to determine the age of the universe or explain the expansion of the universe after instruction. This project is part of a larger study; also see our posters on student ideas about dark matter, the structure of the universe, and perceptions of astronomical sizes and distances. This work was supported by NASA ROSES E/PO Grant #NNXlOAC89G, as well as by the Illinois Space Grant Consortium and National Science Foundation CCLI Grant #0632563 at Chicago State University and the Fermi E/PO program at Sonoma State University.
333.04
Investigating Student Understanding of the Universe: Structure
Virginia Hayes1, K. Coble1, M. Nickerson1, G. Cochran2, C. T. Camarillo1, J. M. Bailey3, K. M. McLin4, L. R. Cominsky4
1Chicago State University, 2Florida International University, 3University of Nevada, 4Sonoma State University.
8:00 AM - 7:00 PM
America Ballroom Foyer
Chicago State University (CSU) offers an introductory astronomy course that services students from a variety of majors including pre-service teachers. At CSU, we have been investigating methods and tools that will improve student conceptual understanding in astronomy for this diverse group of students. We have analyzed pre-course surveys, pre-course essays, exams, and interviews in an effort to better understand the ideas and difficulties in understanding that students have in regards to the structure of the universe. Analysis of written essays has revealed that our students do have some knowledge of the objects in the universe, but interviews inform us that their understanding of the structure of the universe is superficial. This project is a part of a larger study; also see our posters on student ideas about dark matter, the age and expansion of the universe, and perceptions of astronomical sizes and distances. This work was supported by NASA ROSES E/PO Grant #NNXlOAC89G, as well as by the Illinois Space Grant Consortium and National Science Foundation CCLI Grant #0632563 at Chicago State University and the Fermi E/PO program at Sonoma State University.
333.05
Investigating Student Understanding of the Universe: Perceptions of Astronomical Sizes and Distances
Carmelita Camarillo1, K. Coble1, V. Hayes1, M. Nickerson1, G. L. Cochran2, J. M. Bailey3, K. M. McLin4, L. R. Cominsky4
1Chicago State University, 2Florida International University, 3University of Nevada, 4Sonoma State University.
8:00 AM - 7:00 PM
America Ballroom Foyer
Student perceptions regarding astronomical sizes and distances are being analyzed for Chicago State University’s Basic Astronomy course. This area is of great interest to further understand the students’ learning processes and to produce more effective instruction. Insights from cognitive psychology have shown that perceptions are related to prior experiences and current knowledge. Students enter into this course with different mental representations, and these representations can affect their learning. Through a repeated measures design, perceptions are analyzed through several instruments. The instruments implemented are pre-tests surveys (before lab), exams (after lab), lab comments, and interviews. Preliminary analysis reveals that students who have difficulty with astronomical sizes and distances have been more strongly influenced by culture and the media whereas those who had less difficulty expanded on their personal prior experiences. This project is part of a larger study; also see our posters on the structure of the universe, dark matter, the age and expansion of the universe. This work was supported by NASA ROSES E/PO Grant #NNXlOAC89G, as well as by the Illinois Space Grant Consortium and National Science Foundation CCLI Grant #0632563 at Chicago State University and the Fermi E/PO program at Sonoma State University.
333.06
Integration of Galileoscopes into a Large MathMovesU Program
Robert T. Sparks1, C. E. Walker1, S. M. Pompea1
1NOAO.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Galileoscope is a small, low cost, high optical quality telescope kit developed for the International Year of Astronomy 2009. In 2010 and 2011, the National Optical Astronomy Observatory (NOAO) has partnered with Raytheon, the University of Arizona Office of Early Academic Outreach and the Tucson Amateur Astronomy Association to build hundreds of Galileoscopes as part of Raytheon’s Math Moves U program.
Each of these events involved building Galileoscopes with hundreds of students at the same time. We had the assistance of about 70 Raytheon engineers who were participating in the Executive Leadership Development Program (ELDP’s). Prior to the MMU event, the ELDP’s were trained how to build Galileoscopes. One ELDP was stationed at each table of students to help build the Galileoscopes during the event.
The 2010 event involved over 450 eighth grade students from schools in Tucson. The students were predominantly from an underserved population in the Sunnyside School District. The 2011 event reached 350 high school juniors from Tucson, Sierra Vista, and Nogales, Arizona who were part of the GEAR UP program. GEAR UP students come primarily from underserved populations at schools in Tucson, Sierra Vista, and Nogales.
We will discuss the process of planning and running large scale Galileoscope events including planning, logistics, setup, and training volunteers.
333.07
The Flagstaff Star Party Model for Using Galileoscopes: Evaluation Report
Stephen M. Pompea1, R. T. Sparks1, C. Dugan1, E. Dokter2, K. Schindler3
1NOAO, 2University of Arizona, 3Lowell Observatory.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Galileoscope is a low-cost, high optical quality telescope kit designed for education and outreach during the International Year of Astronomy 2009. The Galileoscope has been used in a variety of formal and informal education settings around the world.
We have been developing a model for large star parties by collaborating with school districts and Science Foundation Arizona. We held our first large start party last fall in Flagstaff and have our next one scheduled for April of 2011 in Yuma, Arizona.
The model we are using includes and extensive professional development component for teacher. Each teacher attends a day-long professional development workshop that covers the optics of a telescope, how to assemble a Gaileoscope and how to make astronomical observations. Each teacher receives an optics eduction kit including all the materials necessary to do the activities in their classrooms. The teachers receive Galileoscopes and tripods for their classrooms as well.
Before the star party, NOAO staff visit the classrooms to assist students and teachers with the Galileoscope and to teach observing techniques to ensure all the Galileoscopes are working and can be used at the star party.
The evening of the star party students gather at the site (usually a local park or school grounds) for an evening of observing. Each student tries to find a variety of different objects to get their passports stamped. At the end of the evening, a drawing is held for students who have observed the designated objects.
We will detail the process of planning and holding the star party including professional development, logistics and follow up with the students.
333.08
Engaging the Public in the Citizen Science GLOBE at Night Campaign
Constance E. Walker1, R. T. Sparks1, S. M. Pompea1
1NOAO.
8:00 AM - 7:00 PM
America Ballroom Foyer
The emphasis in the international star-hunting campaign, GLOBE at Night, is in bringing awareness to the public on issues of light pollution. Light pollution threatens not only observatory sites and our “right to starlight”, but can affect energy consumption, wildlife and health. GLOBE at Night has successfully reached a few 100,000 citizen-scientists. What steps can be taken to improve it?
To promote the campaign via popular social media, GLOBE at Night created Facebook and Twitter pages.
To increase participation in the 2011 campaign, children and adults submitted their sky brightness measurements in real time with smart phones or tablets using the web application at www.globeatnight.org/webapp/. With smart phones and tablets, the location, date and time register automatically. For those without smart mobile devices, user-friendly tools on the GLOBE at Night report page were reconfigured to determine latitude and longitude more easily and accurately.
To increase the robustness of the data, 2 new approaches were taken. GLOBE at Night prototyped an “Adopt a Street” program in Tucson. The aim was for people to adopt different major or semi-major streets and take measurements every mile or so for the length of the street. The grid of measurements would canvas the town, allowing for comparisons of light levels over time (hours, days, years) or search for dark sky oases or light polluted areas. The increase to 2 campaigns in 2011 re-enforces these studies. The intent is to offer the program year-round for seasonal studies. The data can also be used to compare with datasets on wildlife, health, and energy consumption. Recently, NOAO and the Arizona Game and Fish Department have started a project with GLOBE at Night data and bat telemetry to examine a dark skies corridor in Tucson where the endangered bats fly.
In our presentation, results of our efforts are discussed.
333.09
The HST Cycle E/PO Grant Program: Program Highlights
Bonnie Eisenhamer1, L. Knisely1, H. Ryer1
1STScI.
8:00 AM - 7:00 PM
America Ballroom Foyer
The spirit of the HST Cycle E/PO Grant Program is to encourage collaborative efforts between professional astronomers/space scientists and professional educators that would broaden the knowledge and understanding of the latest discoveries of the Hubble Space Telescope. HST Cycle E/PO grants provide NASA funding for HST Principal Investigators and Hubble Fellows to develop and implement small E/PO projects based upon the science and/or science theme of the parent research program(s). Awardees do this working in partnership with professionals in the education and outreach communities. Beginning with Cycle 8, 170 science programs have been represented in the HST Cycle E/PO Grant Program. This poster will feature examples of key E/PO projects funded by the HST Cycle E/PO Grant Program, highlighting the aspects that made each one successful.
333.10
Astronomy Education via The Dynamic Web
K. M. Flurchick1, W. Avery1, B. F. Griego2, R. Culver2
1North Carolina A&T State University, 2Colorado State University.
8:00 AM - 7:00 PM
America Ballroom Foyer
The ability of web applications to provide students the ability to explore and investigate astronomical concepts presented in class in a way which can help student understanding. In this presentation we report on the results of students making use of the computational tools in webMathematicaTM to analyze and investigate a variety of astronomical phenomena, including topics such as the Runge-Lenz vector, descriptions of the orbits of the exo-planets and other topics related to celestial mechanics. Using the exercise described herein, students at the North Carolina A & T State University and Colorado State University investigated via computational simulations the creation and characteristics and the
effects of various parameters on these systems being studied.
333.11
Astrobites: The Astro-ph Reader's Digest For Undergraduates
Nathan Sanders1, E. R. Newton1, I. Czekala1, K. Rosenfeld1, C. D. Dressing1, D. Gifford2, J. Suresh1, E. Schneider3, C. Morley4, S. Kohler5
1Harvard University, 2University of Michigan, 3University of Arizona, 4UC Santa Cruz, 5UC Boulder.
8:00 AM - 7:00 PM
America Ballroom Foyer
Do you know an undergraduate embarking on a career in research in astronomy or a related field? Point them to Astrobites, a daily astrophysical literature blog for undergraduates written by graduate students (http://astroph.wordpress.com). Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research. We not only try to summarize new work, but also to provide valuable context for readers not yet familiar with the astrophysical literature. For example, our posts discuss the long term goals motivating the field, astronomical jargon, and how the technical methods work. Special posts offer career guidance for undergraduates (e.g. how to select a graduate school) and detail personal experiences (e.g. observing at a Chilean telescope or attending a AAS meeting). We present sample Astrobites posts, readership statistics, and the results of our periodic reader surveys from our first semester of blogging (Spring 2011).
333.12
Evidence of Historical Supernovae in Ice Cores
Donna Young1
1SAO.
8:00 AM - 7:00 PM
America Ballroom Foyer
Within the framework of the U.S. Greenland Ice Core Science Project (GISP2), an ice core, known as the GISP H-Core, was collected in June, 1992 adjacent to the GISP2 summit drill site. The project scientists, Gisela A.M. Dreschhoff and Edward J. Zeller, were interested in dating solar proton events with volcanic eruptions. The GISP2-H 122-meter firn and ice core is a record of 415 years of liquid electrical conductivity (LEC) and nitrate concentrations, spanning the years 1992 at the surface through 1577 at the bottom. At the National Ice Core Laboratory in Denver, Colorado, the core (beneath the 12-meter firn) was sliced into 1.5 cm sections and analyzed. The resulting data set consisted of 7,776 individual analyses. The ultrahigh resolution sampling technique resulted in a time resolution of one week near the surface and one month at depth. The liquid electrical conductivity (LEC) sequence contains signals from a number of known volcanic eruptions and provides a dating system at specific locations along the core. The terrestrial and solar background nitrate records show seasonal and annual variations, respectively. However, major nitrate anomalies within the record do not correspond to any known terrestrial or solar events. There is evidence that these nitrate anomalies could be a record of supernovae events. Cosmic X-rays ionize atmospheric nitrogen, producing excess nitrate that is then deposited in the Polar Regions. The GISP2-H ice core has revealed nitrate anomalies at the times of the Tycho and Kepler supernovae. The Cassiopeia A supernova event may be documented in the core as well. We have developed a classroom activity for high school and college students, in which they examine several lines of evidence in the Greenland ice core, discriminating among nearby and mid-latitude volcanic activity, solar proton events, and supernovae. Students infer the date of the Cassiopeia A supernova.
333.13
A Comparison of Online and On-Ground Student Performance in Calculus-based Physics I
Andria C. Schwortz1
1Quinsigamond Community College.
8:00 AM - 7:00 PM
America Ballroom Foyer
The validity and rigor of online courses is an open question in higher education, with each institution applying different interpretations of grades received and making different decisions about whether online courses should be accepted in the transfer process. These discrepancies in institutional opinion are at times based upon the realities of variety in instructional methods or student self-selection into a course they view as an “easy A”, but at times they do a disservice to online classes and students.
Quinsigamond Community College, located in Worcester, Massachusetts, is now offering an online section of freshman calculus-based mechanics (General Physics I, PHY 105). During Spring 2011, the author teaches both the online and on-ground sections of the course. Content in the online section is communicated by videos recorded during class sessions in Spring 2010, and both sections perform on-ground labs and take quizzes and exams on-ground.
The author is currently studying student outcomes in the two sections to determine the effectiveness of instruction in the different modalities. Preliminary findings will be presented, including analysis of grades in quizzes, online homework (MasteringPhysics), and labs, and comparisons of student problem solving methods and visual representations of problems (such as Free Body Diagrams). The effect of self-selection will also be investigated using open-ended surveys and pretests. Sample size of the two courses consisted of approximately 20 students online and 25 on-ground, with the students commingled into two lab sections of approximately equal size.
Support for this project was provided by Quinsigamond Community College. This project received approval by QCC's Institutional Review Board; data presented are either in aggregate form, or are used with informed consent of the participants.
334 Dwarf Galaxies Poster Session America Ballroom Foyer
334.01
A Study of Galaxy Properties in the Overlap Between the Sloan Digital Sky Survey and the Arecibo Legacy Fast ALFA Survey
Matthew Dunlap1
1George Mason University.
8:00 AM - 7:00 PM
America Ballroom Foyer
We present optical long-slit spectra for a sample of low surface brightness galaxies selected either from the Sloan Digital Sky Survey (SDSS) or from the HI 21 cm Arecibo Legacy Fast ALFA (ALFALFA) survey. We use these spectra, combined with optical data from the SDSS and HI data from ALFALFA, to contrast the properties of optically selected low surface brightness galaxies with those selected by their HI emission. In particular, we examine the dark matter fractions and star forming properties of the systems. These spectra are also used to assist in understanding the completeness of the combined ALFALFA and SDSS surveys and our ability to match sources between the surveys.
334.02
Metallicities of RR Lyr Stars in Two Fields of the Small Magellanic Cloud
Scott R. Baird1, H. A. Smith2, K. H. Cook3, S. C. Keller4, A. R. Walker5
1Benedictine College and University of Kansas, 2Michigan State University, 3Lawrence Livermore National Laboratories, 4Australian National University, Australia, 5Cerro Tololo Inter-American Observatory, Chile.
8:00 AM - 7:00 PM
America Ballroom Foyer
Two fields in the central regions of the Small Magellanic Cloud have had the metallicities of their RR Lyr stars determined using Caby photometry. The first field, Field 1, was located at 00h 38m, -73o 08’, with about 17 useful RR Lyr stars, while the second field, Field 3, was located at 01h 02m, -72o 24’ with about 13 useful stars. Metallicities were determined for both fields using two different estimates of the reddening, and reddening uncertainty was shown to have little effect on the derived abundances. The best weighted mean values of [Fe/H] were -1.25 + 0.15 for Field 1, -1.23 + 0.19 for Field 3, and -1.24 + 0.11 for the combined fields. The actual spread in the metallicities of the RR Lyr stars in the fields ran from -2.09 to -0.05, significantly larger than the calculated [Fe/H] uncertainties for the individual stars and the standard deviations from the weighted means for the fields. The crowded nature of the fields led to substantial blending difficulties. A subgroup of 9 stars from Field 1 with σ[Fe/H] < 0.30 dex was used as a sample of unblended stars, which gave the weighted mean value of [Fe/H] of -1.38 + 0.20: all stars in this group but one had metallicities between -2.1 and -0.9, and when the single outlier was dropped as a possible unresolved blend the result of [Fe/H] = -1.52 + 0.16 was considered the most reliable. These results indicate a true spread in the metallicities of the RR Lyr stars, suggesting that early in the history of this galaxy there were at least some regions, perhaps very small and localized, perhaps coming from a merger, that had higher than average chemical enrichment.
334.03
The Haverford Variable Star Search project: Segue 2 and Segue 3
Emily Cunningham1, E. Boettcher1, B. Willman1
1Haverford College.
8:00 AM - 7:00 PM
America Ballroom Foyer
The Haverford Variable Star Search project is being conducted with Kitt Peak National Observatory’s 0.9 meter WIYN telescope. The aims of this project include: to better characterize the population of variable stars in ultra-faint Milky Way companions and tidal streams, to capitalize on RR Lyrae stars’ role as standard candles for those systems, and to search for evidence of extended tidal debris around nearby Milky Way companions. During our first observing run, we obtained B, V, and I time-series observations of the Segue 2 and Segue 3 objects over 2 nights. We present the results of this analysis. We thank NSF AST 0908446 for partial support of this work.
334.04
The Field Star Cluster Population in the Starburst Galaxy NGC 5253
Daniel R. Harbeck1, J. Gallagher III2, D. Crnojevic3
1WIYN Observatory, 2University of Wisconsin, 3IfA, United Kingdom.
8:00 AM - 7:00 PM
America Ballroom Foyer
NGC 5253 is a dwarf galaxy that currently undergoes a violent central starburst. While the properties of the central starburst have been studied in great detail, the large-scale picture of the starburst in this galaxy remains unstudied. We present a study of star clusters in the field of NGC 5253, based on HST / ACS observations in the F435W, F555W, and F814W bands. While constraint by three-color photometry, we use STARBURST99 models to derive ages and masses for the cluster candidates, and find our observations to be consistent with an episode of star formation about 1 Gyr ago. that was able to produce thee surviving star clusters with masses between 5 to 10 x 10^5 solar masses. We compare the star cluster populations star formation history to the field star population. For the underlying old field stellar populations, we moreover derive photometric metallicity distribution functions via isochrone interpolation and investigate the presence of stellar spatial gradients.
Share with your friends: |
